Lepldosiren avtlcnlata, Jro7)i Paraguay. 3 



L. artictdata. L. paradoxa. 

 centim. centini. 



Total length 57 57-5 



Disttance of the anus from the tip of the 



snout 401 40 



Distance of the anterior margin of the 



eye from the tip of the snout 2-1 l*o 



Distance of the posterior angle of the 



mouth from the tip of the snout . . 2'5 1'5 



Distance of the branchial aperture from 



the same 6"5 o'3 



Internal distance between the eyes .... 2*4 20o 



Diameter of the eye "3 "3 



Height of the branchial aperture 1 "8 



Length of the anterior extremity 2"6 3"1 



Height of the base of the anterior ex- 

 tremity "4 '2 



Thickness of the base of the anterior 



extremity "2 •! 



Length of the posterior extremity .... 3'8 4'9 



Ileiglit of the base of the posterior ex- 

 tremity '8 'o 



Thickness of the base of the posterior 



extremity '9 -3 



Length of the anal aperture "6 '6 



Circumference behind tiie anterior ex- 

 tremity lo'o 14 



Circumference in front of the posterior 



extremity 16 14 



In the above figures, which have a merely conditional 

 value, differences are seen which are distinctly expressed in 

 the general appearance of the animals. The fact that L. ar- 

 ticulata appears somewhat thicker than L. paradoxa may be 

 due to differences in the state of nourishment or preservation, 

 and is to be disregarded for the present. The differences in 

 the head and in the appendages, on the other hand, are inde- 

 pendent of this. The portion of the head forming the snout 

 is shorter in Lepidosiren paradoxa^ and is more decidedly 

 conical than in the case of L. artictdata', the distance of the 

 eye and of the posterior angle of the mouth from the tip of 

 the snout is smaller in the former than in the latter ; in 

 Lepidosiren paradoxa the posterior circumference of the eye 

 lies almost above the posterior angle of the mouth, while in 

 L. articulata it lies somewhat in front of it. A line drawn 

 from the anterior circumference of the eye horizontally 

 towards the margin of the snout meets this in the case of 

 L. paradoxa at the sloping lateral portion, and is equal in 

 length to four times the diameter of the eye, while in L. ar- 

 ticulata it impinges upon the broad anterior margin of the 

 snout and is six times as long as the diameter of the eye. 

 Owing to the greater distance of the branchial aperture from 



1* 



